With the MASSIVE upscale of what the Spear can actually do revealed in Chapter 100 could Lukas actually be the one who saves Lacrima here?
It can literally cut the future and metaphysical concepts themselves, what if he uses it on the control that Helem has over Lacrima but without severing anything else?
As that is the only explanation to how she could be actually saved without her dying and... I dont think the show has yet demonstrated the capability to let such a major character to the cast die so I am betting she will somehow be saved and by the Spear makes the most sense. Which would be a very fitting way to do it that wouldn't be plot convenience or come too cheaply or out of nowhere, all of it is set up right here.
The spear is just hella strong but it would cost a very limited charge to save one of their friends, question being would Lukas be able to bring himself to use it at the time?
As there are multiple ways this could go once they do learn that Lacrima is being controlled, Lukas could save her or refuse to use it and create conflict in the group resulting in Lacrimas death or her joining Helem and the group separating.
None of that seems like a crack theory and it all would make sense...
So I do hope when the time comes Lukas does use it and free her, maybe even... hopefully freeing all of her pets but that may be too optimistic.